Wave
- In AS/A-level Physics, Cycle = One complete vibration of a wave
- Displacement = How far a point on the wave has moved from its undisturbed position (metres)
- Amplitude = Maximum magnitude of displacement
- Wavelength, 𝜆 = length of one whole wave cycle from two similar points
- Period (T), s = Time taken for a whole cycle to complete or to pass a given point
- Frequency = The number of cycles per second passing a given point
- Phase = A measurement of the position of a certain point along the wave cycle
- Phase difference = Amount that one wave lags behind anotheràmeasured in angles (degrees or radian) or as fractions of a cycle
- In AS/A-level Physics, Reflection = Wave is bounced when it hits a boundary
- Refraction = Wave changes direction as it enters a different mediumàspeeding up or slowing down
- Frequency is the inverse of period
- 𝑇 = 1/f f=frequency T=period Units = 1Hz = 1s-1 $
- Speed of a wave = wavelength x frequency
- 𝑐 = 𝑓𝜆 3x108 for light in a vacuum
- Longitudinal waves vibrate along the direction of energy transfer --> consists of compressions and rarefactions of the medium it travels through (sound)
- Transverse waves vibrate at right angles to the direction of energy transfer --> all EM waves are transverse
- A polarised wave only vibrates in one direction --> only transverse waves behave like this so proof that EM are transverse
- Polarising filters only transmit vibrations in one direction
Polarising glasses uses this effect --> blocks unwanted glare at a certain angle
In AS/A-level Physics, Television and Radio signals are polarised
- Aerial rods are horizontal so they line up with the receiving aerial otherwise the strength of the signal will be lower
- Same for radios --> aligning aerial to transmits and receive
- Superposition = one thing on top of the other --> two or more waves cross, the resultant displacement equals the vector sum of the individual displacement
In AS/A-level Physics, Interference can be constructive or destructive (diagram)
- If crest and trough aren’t same size, then destructive interference isn’t total.
- For the interference to be noticeableàtwo (A) need to be nearly equal
This is the end of the topic!